This invention relates to a magnetically operated constant volume, seal-free reciprocating pump and, more particularly, the invention is concerned with providing a closed system pump having no mechanical coupling between the completely enclosed piston and an external driver allowing contamination free handling and movement of biological fluids as well as fluids used in chromatography, spectroscopy and radiation analysis.
Heretofore, commonly known mechanisms for producing reciprocating motion are usually mechanical and require a reciprocating member such as a crank and connecting rod attached to a piston which necessitates the use of many close fitting parts and include sealing elements to prevent loss or contamination of the pumped fluid. In recent years, various electromechanical pumping devices have been proposed which operate on the principle of magnetics. One commonly used pumping construction includes a piston of magnetic material which is pulled into a magnetic field by a selectively energized solenoid coil. Such structures generally require the use of coil compression springs or the like to cause the return of the piston to its original position after the solenoid coil is deenergized. This creates a serious problem because the springs tend to weaken after extended use and corrosive liquid in contact with the springs can cause damage and failure to occur.
Another problem occurs when it is necessary to handle large volumes of liquid with completely leak-free operation and at the same time to prevent contamination of the pumped fluid by the pump components or the external environment. This requires completely leak-free operation and the proper choice of structural materials. When the pump is to be used as a surgically implanted heart pump, it is necessary that the parts be baked and that they wear indefinitely. Also, where there is need for remote controlled programmable flow of metered amounts of fluid, it is advantageous to provide a moving part of small inertial mass in order to allow substantially instant response to a magnetic drive signal. The hereinafter described reciprocating pump design effectively solves all of the foregoing problems.